DUAL PHASE STEEL SHEET AND MANUFACTURING METHOD THEREOF

摘要

A dual phase steel sheet including: in mass %, C: 0.01 to 0.1%; Mn: 0.2 to 3%; Al: 0.04 to 1.5%; Ti: 0.015 to 0.2%; P: 0.01% or less; S: 0.005% or less; N: 0.01% or less, in which [Ti]−48/14×[N]−48/32×[S]≧0% is satisfied and when Ex.C (%)=[C]−12/48×{[Ti]+48/93×[Nb]−48/14×[N]−48/32×[S]} is set, 0.001≦Ex.C (%)/fsd (%)≦0.01 is satisfied, and a balance being composed of Fe and impurities, in which at the position of ¼ thickness of a sheet thickness, a microstructure is a dual phase with its main phase composed of polygonal ferrite precipitation-strengthened by carbide of Ti and its second phase composed of 1 to 10% in area fraction (fsd (%)) of low-temperature transformation products dispersed plurally, and an average crystal diameter of the low-temperature transformation product is 3 to 15 μm and an average value of a distance of closest approach between the low-temperature transformation products is 10 to 20 μm.

主权项

1. A dual phase steel sheet comprising:
in mass %, C: 0.01 to 0.1%; Mn: 0.2 to 3%; Al: 0.04 to 1.5%; Ti: 0.015 to 0.2%; Si: 0 to 0.5%; Nb: 0 to 0.06%; Cu: 0 to 1.2%; Ni: 0 to 0.6%; Mo: 0 to 1%; V: 0 to 0.2%; Cr: 0 to 2%; W: 0 to 0.5%; Mg: 0 to 0.01%; Ca: 0 to 0.01%; REM: 0 to 0.1%; B: 0 to 0.002%; P: 0.01% or less; S: 0.005% or less; N: 0.01% or less, in which [Ti]−48/14×[N]−48/32×[S]≧0% is satisfied and when Ex.C (%)=[C]−12/48×{[Ti]+48/93×[Nb]−48/14×[N]−48/32×[S]} is set, 0.001≦Ex.C (%)/fsd (%)≦0.01 is satisfied, and a balance being composed of Fe and impurities, wherein
at the position of ¼ thickness of a sheet thickness, a microstructure is a dual phase with its main phase composed of polygonal ferrite precipitation-strengthened by carbide of Ti and its second phase composed of 1 to 10% in area fraction (fsd (%)) of low-temperature transformation products dispersed plurally, andan average crystal diameter of the low-temperature transformation product is 3 to 15 μm and an average value of a distance of closest approach between the low-temperature transformation products is 10 to 20 μm.